Numerous surgical procedures have been developed to replace arteries that have become blocked by disease. The aortocoronary bypass surgery is perhaps the most important of these bypass operations. The coronary arteries supply blood to the heart. As a result of aging and disease, coronary arteries may become blocked by plaque deposits, stenosis, or cholesterol. In some instances, these blockages can be treated with atherectomy, angioplasty or stent placement, and coronary bypass surgery is not required. Coronary bypass surgery is required when these other methods of treatment cannot be used or have failed to clear the blocked artery. In coronary bypass surgery, a vein is harvested from elsewhere in the body and grafted into place between the aorta and the coronary artery below the point of blockage. An illustration of this surgery is shown in FIG. 1, which shows the heart 1 and the right anterior coronary artery 2 and the left anterior coronary artery 3 which supply blood to the heart. The right anterior coronary artery 2 is blocked in its proximal segment at 2a, as shown. This blockage has been bypassed by grafting a segment of vein 4 between the aorta 5 and the distal segment 2b of the right anterior coronary artery 2. Similarly, the left anterior coronary artery 3 may be blocked, and may require bypass with a length of vein 4a between the aorta and the distal segment 3b of the left anterior artery. The operation requires access to the heart, which means that the chest cavity must be opened completely.
The coronary bypass surgery requires a length of vein or artery for the graft. It is preferred to use a vein taken from the patient undergoing the bypass surgery. The patient is a ready source of suitable veins that will not be rejected by the body after transplantation and grafting onto the aorta and coronary artery. The saphenous vein in the leg is the best substitute for small arteries such as the coronary arteries, and it is the preferred vein for use in coronary bypass surgery. This is because the saphenous vein is typically 3 to 5 mm in diameter, about the same size as the coronary arteries. Also, the venous system of the legs is sufficiently redundant so that after removal of the saphenous vein other veins that remain in the leg are adequate to provide adequate return blood flow. The cephalic vein in the arm is an alternative that is sometimes used.
A typical operation previously required to harvest the saphenous vein is illustrated in FIG. 2. The surgeon cuts into the leg to allow access to the saphenous vein and cuts the vein from the leg. To expose the saphenous vein 6, the surgeon makes a series of incisions from the groin 7 to the knee 8 or the ankle 9, leaving a one or more skin bridges 10 along the line of the incisions. Some surgeons make one continuous incision from the groin to the knee or ankle. Handling of the vein must be kept to a minimum, but the vein must be removed from connective tissue that requires some force to remove. After exposing the vein, the surgeon grasps it with his fingers while stripping off the surrounding tissues with dissecting scissors or other scraping instruments. The surgeon uses his fingers and blunt dissection tools to pull and lift (or mobilize) the vein from the surrounding tissue. The vein is mobilized or pulled as far as possible through each incision. To reach under the skin bridges, the surgeon lifts the skin with retractors and digs the vein free. While stripping the vein, the surgeon will encounter the various tributary veins that feed into the saphenous vein. These tributaries must be ligated and divided. To divide and ligate tributaries that lie under the skin bridges, the surgeon may need to cut one end of the saphenous vein and pull it under the skin bridge to gently pull the vein out from under the skin bridge until the tributary is sufficiently exposed so that it may be ligated and divided. When the vein has been completely mobilized, the surgeon cuts the proximal and distal ends of the vein and removes the vein from the leg. After removal, the vein is prepared for implantation into the graft site, and the long incisions made in the leg are stitched closed.
The procedure described above can be used to harvest veins for a femoral popliteal bypass, in which an occluded femoral artery is bypassed from above the occlusion to the popliteal artery near the level of the knee. The procedure can also be used to harvest veins for the revascularization of the superior mesenteric artery which supplies blood to the abdominal cavity and intestines. In this case, the harvested vein is inserted between the aorta to the distal and patent (unblocked) section of the mesenteric artery. For bypass grafts of the lower popliteal branches in the calf, the procedure can be used to harvest the umbilical vein. The harvested vein can also be used for a vein loop in the arm (for dialysis) between the cephalic vein and brachial artery.
As can be seen from the description of the harvesting operation, the harvesting operation is very traumatic in its own right. In the case of coronary artery bypass, this operation is carried out immediately before the open chest operation required to graft the harvested vein into the coronary arteries. The vein harvesting operation is often the most troublesome part of the operation. The long incisions created in the leg can be slow to heal and very painful. Complications resulting from the vein harvesting operation can also hinder the patient's recovery from the entire operation.
The method of vein harvesting presented herein is accomplished with laparoscopic procedures. This allows the veins to be harvested in an operation that requires only a few small incisions. Endoscopic surgical techniques for operations such as gall bladder removal and hernia repair are now common. The surgeon performing the operation makes a few small incisions and inserts long tools, including forceps, scissors, and staplers, into the incision and deep into the body. Viewing the tools through a laparoscope or a video display from the laparoscope, the surgeon can perform a wide variety or maneuvers, including cutting and suturing operations, necessary for a wide variety of surgical procedures and operations.
Minimally invasive procedures for vein removal have been proposed. Knighton, Endoscope and Method for Vein Removal, U.S. Pat. No. 5,373,840 shows a method of cutting the saphenous vein at one end, and grasping the vein with graspers or forceps, then sliding a ring over the vein while holding it. Knighton uses a dissecting tool with an annular cutting ring, and requires that the saphenous vein be overrun or progressively surrounded with the dissecting tool and the endoscope, so that after the endoscope has been inserted as far as it will go, the entire dissected portion of the vein has been pulled into the lumen of the endoscope. As shown in FIGS. 1 and 10 of Knighton, the method requires deployment of forceps inside the annular dissection loop, and it requires deployment of the loop and graspers inside the endoscope lumen. The blood vessel must be cut and grasped by the forceps before it can be dissected by the dissecting ring.
The method of vein harvesting disclosed herein uses a balloon to assist in dissecting the harvested vein. An uninflated tubular balloon wrapped around a guide rod or endoscope and covered with an easily removable balloon cover is inserted into one of the small incisions and pushed along the vein to create a small tunnel over the vein. When the balloon is in place over the vein, the balloon cover may be left in place or it may be removed and the balloon is inflated to enlarge the tunnel and create a work space for insertion of endoscopic instruments. The guide rod or endoscope may be removed to allow other endoscopic instruments to be passed into the tunnel through the balloon.